The instant invention relates to construction techniques and more particularly to a method for underpinning an existing footing so that a new foundation portion may be constructed directly beneath the footing.
In the restoration of old buildings it is often necessary to construct a new foundation portion underneath an existing footing in order to support the building structure. One problem associated with installing a new foundation portion is that the existing footing of the building structure must be supported while the ground underneath the footing is excavated to make room for the new foundation portion. In order to be effective in supporting the building load, the new foundation portion should be constructed directly below the existing footing so that the existing footing rests directly on the new foundation portion. However, the heretofore known methods and apparatus for underpinning a building structure typically include one or more bracing or support members which are installed underneath the footing in order to support the footing while excavation takes place. In this connection, the U.S. Patents to Bullivant U.S. Pat. No. 4,834,582; Hamilton et al U.S. Pat. No. 5,011,336; and Freeman III U.S. Pat. No. 5,116,355 represent the closest prior art to the subject invention of which the applicant is aware. Each of the above-referenced patents discloses an underpinning system in which support elements are installed beneath the footing in order to support the footing during excavation. It can be seen that the support elements of the prior art interfere with the excavation processes and further interfere with the construction of a new foundation portion beneath the footing. More specifically, the new foundation portion must be constructed in pieces or sections in order to fit around the underpinning support members.